The likelihood of lightning striking an object is increased if the object is tall as this causes the equipotential lines found parallel to the earths surface to be closer together as they bend around the object.This causes the potential gradient here to be greater which makes the path to taller objects easier and so the lightning often takes it. This is the reason that buildings and more specifically tall buildings need protection against lightning strikes.

If the lightning is to hit the building then it can not only damage the structure but it can also fry the electrics which would be very expensive to replace.

Two main types of protection are studies below.

Benjamin Franklin (1706-1790)

Lightning Rod

The lightning rod was first invented by Ben Franklin in 1752.The aim of this lightning protection system is to neither repel nor attract the strike but to simply redirect it on a safe, specified, low resistance path to the ground.

The use of lightning rods has been very popular as an inexpensive way to protect millions of homes from being damaged.

According to research dne by the University of Florida these rods have different effectiveness according to the soil type as rods which are earthed to sandy soils do not conduct as much current as they are expected to. This means that by trying to force current down this rod which can not cope there will be damage caused to the building unless further protection is taken, for example surge protectors.Another alternative is that instead of the usual vertical rod the current is sent to a large ring circling the building which, due to the increased area, is more effective at dissipating the electricity.

Over all the use of lightning rods is very successful and the combination of this and a surge protector will usually suffice to certainly greatly reduce the damage that would have been caused if the building had not been protected.

Franklin's Bells

This is a fairly simple warning system developed using Franklins knowledge of the high levels of voltage present during a thunder storm.

It is this high voltage present which causes enough current to want to flow in the circuit that the ringer fluctuates back and forth, transferring the charge and making the bells ring. The apparatus of this device is shown below.

This method gives little time for real action to be taken if precautions have not already been arranged.